linux-kernel - Re: [PATCH RFT 03/14] drm/msm/adreno: Offset the HBB value by 13

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Message-ID: <eddc2ea5-dab7-4c9c-89fd-23ed20b85ecc@oss.qualcomm.com>
Date: Fri, 9 May 2025 14:30:23 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Connor Abbott <cwabbott0@...il.com>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>, Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org
Subject: Re: [PATCH RFT 03/14] drm/msm/adreno: Offset the HBB value by 13

On 5/8/25 9:03 PM, Connor Abbott wrote:
> On Thu, May 8, 2025 at 2:13 PM Konrad Dybcio <konradybcio@...nel.org> wrote:
>>
>> From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
>>
>> The value the UBWC hardware expects is 13 less than the actual value.
>> To make it easier to migrate to a common UBWC configuration table,
>> defer that logic to the data source (which is currently a number of
>> if-else statements with assignments in case of this driver).
> 
> Don't break the value exposed to userspace!

Bah, I keep forgetting it's there.. I think I'll alter the mdss code to
do a -13 in there instead to make it a little saner with the future
getters that return the x+13 value too.

Konrad